Controllable draft for tunnel-kilns.



J. B. OWENS.

CONTROLLABLE DRAFT FOR TUNNEL KILNS.

APPLICATION FILED MAR. 3. 1911.

il wfiwo Patented Dec. 31, 191&

4 SHEETS-SHEET l.

J. B. OWENS.

CONTROLLABLE DRAFT FOR TUNNEL KILNS.

APPLICATION FILED MAR. s. 19H.

ma ma Patented Dec. 31, 1918.

4 SHEETS-SHEET 2.

J. B. OWENS.

CONTROLLABLE DRAFT FOR TUNNEL KILNS.

APPLICATION r1120 MAR. 3, 1911.

189 8891 Patented Dec.31,1918.

4 SHEETS-SHEET 3.

lmvwmooe J. B. OWENS.

CONTROLLABLE DRAFT FOR. TUNNEL KIVLNS.

lygggpgggo APPLICATION FILED M'AR. 3. I911 Patented Dec. 31

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JOHN B. OWENS, 0F METUCHEN, NEW JERSEY.

CONTBOLLAQBLE DRAFT FOR TUNNEL-KILNS.

Specification of Letters Patent.

Patented Dec. 31, 1918.

Application filed March a. 1917. Serial No. 152.444;

.The molding of a piece of pottery, tile,

or brick requires the presence of a certain quantity of water in the rawmaterial. The next step is to slowly dry the molded article until allsuspended moisture is'eliminated so that the central portion of thepiece will become dry before the outer surface commences to harden. Ifthe-outer surface hardens before'the moisture is eliminated from thecentral portion of the piece, a crack necessarily develops to liberatesteam generated inside the piece. Another critical point is reached atthe temperature when what is commonly known at water of combination isliberated. To raise the piece to either of these critical temperaturestoo rapidly, invariably results in damage or total loss of the article.

In a tunnel kiln the exact temperatures therein at the critical pointsabove mentioned, may vary somewhat according to the nature of thematerial being burned and 'its rate of progress through the tunnel.

Thin material, such as floor tile, can be heated much more rapidly thanbrick or heavy pieces of pottery which may contain more "suspendedmoisture than tile and require more time for heating the mass.

Weather conditions, rate of production, and other considerations mayrender it necessary from time to time to change the rate at which heatis applied to or withdrawn from the kiln in order that uniformconditions may be maintained inside the kiln at different points of thelength thereof.

The nearest to an ideal condition would be a constant rate of firing anda uniform travel through the kiln of the material to be burned. Themaintenance of fire at a constant degree of intensity and constant rateof fuel consumption contributes to thermal efiiciency and economy oflabor and supervision. A certain minimumtempera- B Owens, a

ture is the lowest at which a given ware can be finished and there is amaximum temperature going beyond which will result in overburning anddamage.

The economy of operation of a tunnel kiln depends largely upon theextent to which the heat contained in the products of combustion fromthe furnace can be absorbed before these products of combustion reachthe stack on other draft inducing means. If the material is conveyedthrough the tunnel with suflicient rapidity to absorb a maximum amountof the heat liberated from the furnace, too rapid heating of the waremay result, with consequences as previously described.

' To obtain the desired graduation of heat at diflerent points at itslength, a tunnel kiln might be built of a length suflicient to give thedesired stack temperature at the 'proper rate of progress" of the warewithin the tunnel. Great length of a tunnel kiln increases the cost ofinstallation and raises the investment to a point where there is 'no Itis not practicable to change the rate of travel of the conveyor, onceits rate has been determined, nor to locate the point of maximumtemperature where more rapid heating could be effected after passing thepoint of critical temperature, because the kiln could then only be usedfor one class ofware and, furthermore, the furnace might have to belocated so near the stack or draft inducing means as to reduce thethermal efliciency of-the kiln below the point dictated by commercialrequirements.

If the "introduction of heat at difierent points along the tunnel isresorted to in order to secure the desired distribution, serious stacklosses and inconvenience in operation result and such method isparticularly impracticable where the fuel. is wood or coa The successfuloperation of any kiln for burning ceramic ware, or material made fromclays, once the required heat has been.

attained in the furnace, depends largely upon the rate" at which thematerial being burned is brought up to its maximum heat, also upon therate of cooling. Heat control is necessary also in annealing, hardening,and metallurgical operations, as well as in certain processes in themanufacture of glass ware.

lhe foregoing enumeration of conditions met with in practice in theoperation of tunnel kilns, clearly shows the advantages of a kiln whichcan be standardized to handle a variety of ware without necessitatingchanges in the construction of the kiln when a change is made from theburning of one class of ware to another class, and which enables thekiln to be of comparatively short length so that the first cost ofconstruction is comparatively low and the space required is not so greatas to prevent the use of the kiln in industrial operations in thoselocalities where space is costly.

The kiln constituting the present invention possesses the advantagesjust enumerated, is simple in construction and operation, and may besuccessfully operated without expert labor or supervision. The desiredobjects are accomplished entirely by manipulation of the draft, thefurnace or source of heat of the kiln being maintained at thetemperature which is required for the finishing of the material to beheated or burned. At different points of the length of the tunnel,between the furnace or source of heat and the stack or draft inducingmeans, the

, tunnel is provided with openings, controlled by dampers, leading intoa flue or flues connecting with the stack whereby heat maybe taken offfrom the tunnel at whatever point first critical temperature and ifenough heat be taken from the tunnel at a point or points between thefurnace and the stack, to reduce the temperature of the tunnel at apoint opposite the stack below the temperature of the stack itself, thethermal efliciency of the kiln would be seriously impaired, unlessindeed, a comparatively elaborate system of heat absorbing devices, suchas waste heat boilers, or similar apparatus, is installed. Furthermore,the graduation of heat simply by allowing the escape thereof from thetunnaeaeee ately' at the entrance of the kiln and gradually increasefrom that point on, as the ware travels in the kiln. By forcingsuflicient draft beyond the main outletor out the kiln to renderpossible the comparatively slow heating of the ware until the firstcritical temperature has been passed, the thermal efficiency of the kilnis greatly increased andthe rapidity ofproduction is enhanced.

I may provide, as shown in one form of the klln disclosed in thedrawingsand hereinafter described, additional main draft fines andregulating dampers for-the purpose of increasing the pull of the drafttoward the entrance end of the kiln, thus, in

lets to the stack, toward the entrance end of eflect, increasingthecapacity of the stack by I the elimination of counter currents in theconnection from the kiln to the stack. A double draft outlet from theentry end of the kiln is thus provided. 3

In tunnel kilns it has been customary to provide a sand seal to shut offthe heat in the tunnelso that it will not have access to the under partsof the appliances, for instance cars, which carry the ware being burnt.Such cars are usually provided with a protecting platform of refractorymaterial. The integrity of sand seals is. diflicult to ma ntain.

My kilnmay be provided with means by which a sufliciently lowtemperature may be maintained below the platforms of the cars to preventinjuryto the trucks and other mechanical parts, whereas the space abovethe car platforms will be maintained at the temperature required forburning the ware. This eliminates the necessity of a sand seal andsimplifies both the construction and operation of the kiln. Toaccomplish this object I provide means by which inert air is maintainedbelow the car platforms as an insulator from the ,heat above saidplatforms and supplements the insulating action of the protectiveplatforms. The inertness of the air in the space below the platforms isoccasioned by sealing that space from the outside air and preventing itfrom having direct connection with the draft outlet to the stack exceptby air leakage through the space between the tunnel walls and theedgesof the refractory car platforms, and the spaces between the cars. Whenit is .de-'

- iaeaeee sired to take advantage of the air leakage referred to and tocirculate enough air under the car platforms to cool the working partsof the cars, communication between the space below the car platforms andthe outside air is established by operating dampers controlling inletopenings whose number may vary according to requirements. The airleakage in question, while not interfering with conditions to bemaintained above the car platforms, will have sufiicient cooling effeetto prevent the accumulation of injurious heat below the car" platforms.In my Patent No. 1278991, Sept. 17, 1918, I'have set forth and-claimedthose features of the present invention which relate to the method of,and means for, sealing the space below the car platforms from the spaceabove them by an air curtain and to the balancing of the draft by airleakage.

When I refer to car platforms, 1 have reference to any eonveyer supportor platform on which the ware is carried; cars are commonly employed forthat purpose, but other conveying means could be used.

Control of the rate of cooling in my tun nel kiln after the maximumburning temperature has been attained is of importance as well ascontrol of the rate of rise to maximum temperature. The rate of coolingis not controlled directly by the draft although regulation of the drafthas a certain effect which is taken into consideration.

The embodiments of the invention shown in the drawings and hereinafterdescribed are to be consldered as illustrative, rather than restrictive,of the scope of the invention, as other forms may be resorted to withoutchanging the essential principles thereof.

In the accompan ing drawings:

Figure 1 is a alf plan, half sectional view, of a kiln, certain partsbeing broken away, and others shown in dotted lines;

Fig. 2 a side elevation with certain parts in section;

Fig. 3 an enlarged detail section on line 33 Fig. 1;

Fig. 4 a similar view on line 44;

Fig. 5 a like view on line 55;

Fig. 6 a corresponding view on line 6-6;

Fig. 7 a detail side elevation of a portion of the kiln showing amodification having a double draft outlet;

Fig. 8 a horizontal section thereof.

Fig. 9 a section on line 99 Fig. 8; and

Fig. 10, a section on line 10-10, Fig. 8.

The kiln has an air-lock 1 whose doors.

are shown at 2 and 3. After the ware has passed from the lock 1 underthe door 3, it is in the kiln proper 4 and is heated until it reaches apoint opposite the furnaces 5. The ware is cooled as it passes beyondthe furnaces 5 into the cooling zone 6, thence into the air-lock 7having doors 8 and 9 and finally out of the end of the kiln, thedireciii on of travel being shown by the arrow in The stack 10 may belocated immediately afdjacent the kiln or at a point removed there- Whenreferring to the stack in the following description and claims, I am tobe understood as including any means for inducing draft and that termmay comprehend a plain stack, a fan, or a combined fan and stack, or,any means for inducing draft. Referring first to Figs. 1, 2 and 5, thestack communicates with the kiln proper 4 by a flue or duct 11,"and downflues 12 and 13 which are 'oined to the kiln by ports or openings 14.ampers 15 of the slide, butterfly, or any other type, controlcommunication between the ports 14 and the main flue 11. The regulationof these dampers enables the main draft from the kiln through the 85ports 14 to .be changed, as desired, irrespective of the controls now tobe described.

Extending alongside the kiln on its opposite sides are flues 16 whichopen into the main draft flue 11 below the dampers 15, so that'there isno interference with regulation by'the dampers-.15 of the main draft. Atintervals the opposite sides of the kiln are provided with outlets orports 17 atpoints between the main draft outlets 14 and the furnaces 5.The size and number of these outlets 17 may vary according toconditions. Each outlet is controlled by a damper 18'of any desiredtype, enabling the regulation of thedraft to becarried on at any pointor points desired.

My invention does not solely comprehend the provision of theseadditional outlets 17 opening into the lines 16, but as I have pointedout previously, it comprises draft outlets 1'05 19, of any desirednumber, leading from that portion of the kiln proper 4 which is locatedin advance of the main draft outlets 14 and between said outlets and theentry portion of the kiln,-said outlets 19 leading 110 to flues 20 whichcommunicate with the down flues 12 below the dampers 15. Any suitabledampers 21 are provided for the outlets 19 so that any desired controlthereof may be obtained. As previously explained, the even 115graduation' of heat in the tunnel through a wide range of temperaturesis obtained, .not alone by the use ,of the outlet 17 and dampers 18, butby drawing the heat beyond the main draft outlets 14, that is, into theentry slow heating of the material is had until the first criticaltemperature has been passed and the thermal efliciency of the kiln isgreatly increased and rapidity of production is promoted Waste heattaken from the kiln may be utilized as a heating medium for heat absorbing instrumentalities such assteam boilers 22 as explained morefully in my application, Serial No. 142675. It is possible to utilizewaste heat taken from points between the tunnel and the stack in otherlower temperature waste heat absorption systems, such as driers,sanitary incinerators, heating systems for buildings and the like. In myapplication Serial No. 142674 I have set forth a sanitary incineratorand a method for incineration in that connection. These wvaste heatappliances do not affect the principles of draft control, but they arementioned because they contribute to the over-all thermal efficiency ofthe plant in connection with the system of heat control.

Referring to Fig. 6 there may be provided in the arch 23 of the kiln oneor more openings 24 which are connected in any suitable manner by a flueor flues 25 with the stack 10. A damper 26 controls the draft throughthe opening 24and flue 25, in each instance. These outlets each havedraft control similar to the outlets 17,; and 19.

By adjusting the dampers 15, the draft 7 the required temperature hasbeen reached at the entrance of the kiln and the necessary graduation ofthe temperature obtained between the entrance and the main draft outlets14.

In Figs. 7, 8, 9, 10, there is shown a modified construction andarrangement of fiues and damperswhereby a stronger pull of the drafttoward the entrance end of the kiln may be obtained. The effect obtainedis practically equivalent to an increase in the stack capacity by theelimination of counter currents in the connection from the kiln to thestack. The outlets 17 and 19 and their dampers are the same as in Fig.1,

and open intothe respective flues l6 and 20 which have diving flues 27and 28 connecting the flues 16 and 20, respectively, to the stack 10. Inaddition to the outlets 17 and 19 there 'are provided outlets 29 and 30which are provided with horizontal dampers 31 to control the draft fromthe body 4 of the kiln into the stack 10 independently of the otheroutlets. The outlets 29 and 30 communicate with the same trunk flue s'32 and 33 with which the diving flues 27.and 28 communicate. Stackcut-off dampers 34 and 35 control communicationbetween the trunks 32 and33 and the stack 10. By opening or closing the damper 34 the draft fromthe flues 16 and outlets 29 maybe regulated independently of theregulation of the draft from the entrance end of the kiln body 4 intothe stack 10 by way of the outlets 19 and 30, and vice versa. I

, Referring to Fig. 5, it will be seen that the outlets 14 (andlikewiseoutlets 17, 19, 29 and30) are located above the refractory platform 36of the car which carries the ware 37 and that the edges of said platformtravel in channels 38 in the walls of the tunnel. The wheels 39 run onrails 40. The mechanical partsof thecar or conveyer are, therefore,located in a space 41 below the platform 38, said-space being filledwith inert air which acts as an insulator from the heat in the upperportion 42 of the tunnel. Theinertness of the air inthe space 41 isduetothe fact that this space is sealed from the outside air and has nodirect connection with any draft out-let, except by leakage around theedges of. the platform 36- where they loosely project into the channels38. 95

In the floor 43 of the kiln there are provided openings 44 and 45 (Figs.1 and 3) which are controlled by dampers 46 and 47, respectively.Usually one or two of these Openings is suificient, but their number maybe increased according-to the requirementsunder which the kiln is to beoperated. v Outside air may be supplied to' the openings in anypreferred manner, .a convenient plan being the provision of inspectiontunnels 48, 49,- Figs, 1, 2, 3. These tunnels 48, 49 may communicatewith several kilns. By suitable adjustment of the dampers 46, 47, it ispossible to maintain a circulation of air from the space below theprotecting platform 36 upwardly through; the points of leakage from thespace 41 to the space 42 at a rate which will not interfere withconditions tobe maintained above the platform 36, but which will havesufiicient cooling 115 eifect to prevent the accumulation of injuriousheat in the space 41 below the platform.-

In that connection, it is to be noted that however well the mechanicalparts below the platform 36 may be insulated by the said 120 platformand the inert air space 41, it might be possible .to accumulateinjurious heat in the space 41 under extreme conditions, if it were notpossible to renew the supply of air either at intervals or continuously,at; the 125 proper rate. I

By thus dividing the tunnel into upper and lower strata, comprising anupper section in which burning operations are conducted at hightemperature, and a lower 130 aeaeee section containing the mechanicalparts for carrying the ware, the'temperature in the lower section beingmaintained at a sufiiciently low point not to injure said mechanicalcarrying parts, a balanced condition exists between the upper and lowersections which prevents downward draft from the higher to the lowertemperature and renders possible the admission from below of sufficientcool air to maintain the low temperature required in the lower section.This balancing of the draft renders unnecessary the provision of sandseals or means to hermetically sealthe upper section from the lowerzone.

The controllable draft for regulating the temperature at the entry endof the kiln, includes not only the regulation of particulartemperatures, but also the regulation of velocity of the draft. 7

Serial No. 109511, filed In an application, July 15, 1916, I havedisclosed and claimed inspection tunnels and channels, openings, anddampers for the control of the an admitted to the bottom of the tunnel;and in my Patent No. 1246148, dated Nov. 13, 1917, I have claimedcertain improvements thereon.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is 1. A tunnel kiln having a continuous openinterior throughout its active length from the point where the wareenters to that where it leaves the active length of the kiln andnormally closed at its entry portion, a

main draft outlet connecting with the kiln at a point inwardly oft-henormally closed entry portion of the active length thereof, and acontrollable draft outlet for the active entr portion of the kilnbetween the main dra outlet and the point where the ware enters thekiln, and means whereby direct draft may be caused to pass through theactive length of the kiln and out through the draft outlets aforesaid.

2. A. tunnel kiln having a continuous open interior throughout itsactive length from the point where the ware enters to that where itleaves the active length of the kiln and normally closed at its entryportion, a main draft outlet connecting with the kiln at a pointinwardly of the normally closed entry portion of the active lengththereof, a controllable draft outlet for the active entry portion of thekiln between the main draft outlet and the point where the ware entersthe kiln, and another controllable draft outlet connecting with the bodyof the kiln inwardly of the length of the kiln beyond the main draftoutlet aforesaid, and means whereby direct draft may be caused to passthrough the active length of the kiln and out through the draft outletsaforesaid.

3. A tunnel kiln having a continuous open interior throughout its activelength from the point where the ware enters to that where it leaves theactive length of the kiln and normally closed at its entry portion, amain draft outlet connecting with the kiln at a point inwardly of thenormally closed entry portion of the active length thereof, a pluralityof draft outlets for the active entry portion of the kiln between themain draft outlet and the point where the ware enters the kiln, dampersfor the respective ones of the plurality of draft outlets whereby thedraft through the different ones may be independently controlled, andmeans whereby direct draft may be caused to pass through the activelength of the kiln and out through the draft outlets aforesaid.

4. A tunnel kiln having a continuous open interior throughout its activelength from the point where the ware enters to that where it leaves theactive length of the kiln and normally closed at its entry portion, acontrollable main draft outlet connecting with the kiln at a pointinwardly of the normally closed entry portion of the active lengththereof, a plurality of draft outlets for the active entry portion ofthe kiln between the main draft outlet and the point where the wareenters the kiln, dampers for the respective ones of the plurality ofdraft outlets, whereby the draft throu h the different ones may beindependently controlled, a plurality of draft outlets oonnectin withthe bod} of. the kiln inwardly 0f the length of the kiln beyond the maindraft outlet aforesaid, dampers for the respective ones of the draftoutlets last-named, whereby they may be independently controlled, andmeans whereby direct draft may be caused to ass through the activelength of the kiln and out through the draft outlets aforesaid.

5. A direct draft tunnel kiln having a continuous open interiorthroughout its active length from the point where the ware enters tothat where it leaves the active length of the kiln and normally closedat its entry portion, said kiln being provided with a main draft outlet,and means for controllably forcing or surging the heat by direct draftinto the normally closed entry portion of the kiln beyond the main draftoutlet, whereby the ware may be subjected to a predeter mined gradualheating effect when it enters the kiln.

In testimony whereof, I hereunt aflix my signature.

' JOHN B. OWENS.

